1. Field of the Invention
The present invention relates to improvements in an exposure controlling device for a camera.
2. Description of the Prior Art
In a known electric shutter according to the prior art, the time constant of a shutter circuit is determined by designating an aperture in advance so that the shutter speed is set in accordance with said time constant and object brightness information. In a known program electric shutter requiring no designation of the aperture, the shutter also acts as the aperture so that the shutter blades are closed again before they are fully opened in case the object brightness is sufficient. The former shutter is troublesome because the aperture has to be designated in advance, and the latter shutter is restricted to the lens shutter.
In a known program type electric shutter which is not restricted to the lens shutter, on the other hand, the aperture and shutter speed, which are programmed in advance, are determined in accordance with the object brightness, or the aperture is set in accordance with the object brightness so that the shutter time second may be determined in accordance with the aperture and object brightness determined. In the former shutter, the aperture and shutter speed are determined in parallel in accordance with the program. However, it is difficult to actually set the aperture and shutter speed accurately at the programmed values. There arises a problem, in which the device not only becomes complex but also requires much time period for its setting. In the latter shutter, on the other hand, the aperture is first determined so that the shutter speed is determined in accordance with the aperture and object brightness determined. As a result, the setting of the aperture does not require such accuracy as the former shutter thereby to make it possible to raise the aperture setting rate. Since, however, the shutter speed is determined after the aperture setting is performed by the mechanical operations which require more time period than the electrical information processing, the latter shutter encounters the problems that the setting of the exposure conditions as a whole also requires considerable time period and that an aperture setting device for setting the aperture in accordance with the object brightness becomes considerably complex.